1. Field of the Invention
This invention relates to sealing devices for sealing the chimney, cone and/or base of manholes and more particularly, to a method and apparatus for sealing manholes using a manhole seal which includes a removable manhole insert. The apparatus for sealing manholes is characterized by a manhole seal which includes a generally donut-shaped seal structure that is mounted in the chimney, cone or base directly to the wall of the manhole at a selected distance from the manhole opening. In a preferred embodiment, a seal structure component of the manhole seal is constructed in the manhole by initially mounting a resilient form base to the manhole wall at a selected depth in the manhole, which form base conforms to the shape of the chimney, cone or base of the manhole and can be utilized in both concentric and eccentric, as well as concrete and brick manhole structures. A temporary form is then placed on the form base to define an annulus between the manhole wall and the temporary form and facilitate pouring concrete in the annulus, to define the seal structure. A seal or gasket is then seated on or embedded in the concrete while the concrete is wet, for sealing the manhole insert element of the manhole seal on the seal structure, as hereinafter described. The temporary form is then removed, leaving the seal structure in place and the dish of a dish-shaped manhole insert is positioned in the opening defined by the seal structure, with the rim or flange of the manhole insert resting on the seal structure or on the seal or gasket which is seated in or resting on the seal structure.
In many municipal sanitary sewer manhole installations the seal at the corbel joint between the flange of the manhole frame and the upper portion of the manhole masonry chimney is frequently broken from vibration due to traffic and/or temperature changes, leaving a crack where surface water may flow into the manhole. This leakage of surface water, coupled with sub-surface storm water and/or ground water which enters the sanitary sewer system through cracks in the chimney structure, frequently causes overflow conditions at waste treatment plants during or shortly after rainstorms.
In a conventional manhole structure, the manhole frame is typically fabricated of cast iron and is mounted immediately below the surface of a street or roadway to serve as a seat for manhole cover. The casting is supported by the manhole chimney, which may be constructed of concrete or brick masonry and is frequently found to be in a highly deteriorated condition due to vibration, water leakage, freezing and thawing, as well as corrosive attack by sewer gases. Accordingly, water from drainage of both surface water and sub-surface storm water, as well as ground water, flows through the corbel joint and the deteriorated chimney into the manhole and from the manhole into the sewer system, frequently overtaxing the sewerage treatment system. Since the capacity of a sewerage treatment system in large part is a measure of the volume of the effluent which can be treated, water infiltration during sudden rainstorms or during periods of extended rainfall activity add to the total volume of effluent treated. This increased volume of water may overload both new and old sewerage treatment systems and in most cases, the excess volume of effluent overload is dumped untreated into rivers and lakes.
Another problem which results from surface water infiltration into manholes is the flow of contaminated surface water, especially when the contaminant is a petrochemical or a dangerous manmade pollutant, such as PCB. Contaminated surface water which infiltrates the sewerage system through a manhole will be distributed to other sites by the sewerage lines to which the manhole assemblies are connected. Consequently, a contaminant that should be contained and safely removed from population centers may instead be widely dispersed in an uncontrolled fashion through a sewerage system.
Accordingly, there is a continuing need in the field of manhole construction for an apparatus to seal the manhole against both surface and sub-surface water, including ground water. There is also a need for a removable seal which is effective against water infiltration occurring in the manhole cover and vent or pick hole areas in the area between the casting and the supporting chimney structure and through the chimney structure, cone and base of the manhole. There further exists a need for a manhole seal that can accommodate vertical and horizontal displacement of the casting relative to the supporting masonry structure during prolonged use, which seal is removable for replacement or to allow maintenance in the manhole structure itself.
2. Description of the Prior Art
Various types of structures have been proposed in the art for sealing manholes in order to prevent, or at least minimize, the leakage of surface water and sub-surface water into manholes. Typical of this art is the manhole chimney seal detailed in U.S. Pat. No. 4,469,467, dated Sept. 4, 1984, to Frank J. Odill, et al. The patent details an internal seal which is located between a manhole casting and mating manhole components, such as concrete adjusting rings, the concrete manhole cone, or masonry structure of a similar configuration, to prevent water infiltration at this interface. The seal is formed by a continuous elastomeric ring, which ring is held in place by two stainless steel retaining bands. The ring is pleated to allow upward or lateral movement of the casting without impairing the sealing ability of the ring. The gasket can be installed either during construction or at any time after construction where there is found to be a problem with water infiltration. U.S. Pat. No. 4,475,845, dated Oct. 9, 1984, details an "External Manhole Chimney Seal". As detailed in this patent, a cylindrical elastomeric seal is designed to externally seal a manhole assembly against surface water infiltration between the manhole casing and the supporting structure, as well as through the supporting structure. The seal has a first sealing section adapted to receive the edge of the flange of a manhole casting, a second sealing section adapted to be received by the external surface of the manhole chimney or cone, and an intermediate section joining the first two sealing sections, for spanning the vertical distance between the casting and the chimney or cone. A sealing mechanism holds the two sealing sections in place against the casting and chimney, to create water-tight seals. An extension skirt increases the effective sealing area cover, allowing the entire supporting structure to be sealed under circumstances where the chimney height is too great to be spanned by the intermediate section of the seal alone. The seal can be used on old or new construction and does not interfere with normal use of the manhole. An "Internal Sealing Assembly" is detailed in U.S. Pat. No. 4,577,625, dated Dec. 10, 1985, to Richard P. Jahnke, et al. The sealing assembly includes a tubular rubber sleeve having an axial link sufficient to span the joint between hollow members, such as the corbel joint between a manhole frame and a manhole casing, and the sealing portion in each of the opposite ends. The outer surface of each sealing portion is compressed radially outwardly in sealing engagement with the interior walls of the manhole frame and the manhole casing, by a generally circular hoop which fits into a groove provided on the inside surface of the sleeve. Each hoop has circumferentially movable end portions and a radially inwardly-extending bracket mounted on each end portion at circumferentially spaced locations. These brackets are adjustably pulled toward each other to increase the circumference of the hoop by tightening a nut threaded onto the outer end of a bolt connecting the brackets. The distance between the outer ends of the bracket can be adjusted to maintain the brackets substantially parallel during tightening, by turning a nut threaded onto the outer end of a threaded member spaced radially inwardly from the tightening bolt and connected between the brackets. U.S. Pat. No. 4,582,449, dated Apr. 15, 1986, to Gilbert Vosswinkel, details a "Manhole Sealing Device". The manhole sealing device further details a method for sealing a frame-chimney joint between a manhole chimney and a manhole cover frame and includes an annular ring defining a narrow annular space adjacent to the frame and the chimney and across the frame chimney joint and a flexible, water-resistant cement filling the annular space and adhering to the annular ring, the frame and the chimney. In one embodiment the ring includes a plurality of ring segments which are held together by slip joints and the ring includes an expansion joint to permit the adjustment of the annular space. The annular ring further includes multiple, horizontal retainers secured in the frame-chimney joint for securing the ring adjacent to the frame in the chimney. U.S. Pat. No. 4,608,787, dated Sept. 2, 1986, to Franklin J. Carlson, details a "Manhole Seal Construction". The manhole seal construction is designed to engage the outer surface of the manhole frame and chimney to seal the corbel joint from the outside and prevent leakage of water and entry of foreign material into the joint and manhole. A resilient ring having a hook-like upper section is engaged with the outwardly-extending flange on the manhole frame and the ring has a thin, stretchable central section which extends across the corbel joint. The lower portion of the ring terminates in a lower section having a series of internal ribs that seal against the chimney and having an outer circumferential groove to receive a clamping band. To provide additional sealing, an annular sealing gasket is bonded to the internal shoulder on the manhole frame and the manhole cover seats on the gasket to prevent leakage from the street into the manhole through the joint between the cover and the frame. U.S. Pat. No. 4,737,220, dated Apr. 12, 1988, to Jack Ditcher, et al, is entitled "Method of Making A Manhole Riser Having Integral Flexible Waterlock for Manhole Covers and Having a Water-Tight Seal for Sealed Manhole Covers". The device detailed in this patent includes a hollow, flexible, bendable, cylindrically-shaped, hat-like sleeve which is water-tightly joined to the upper end of the riser section of a manhole structure. The free end of the sleeve is trimmed so that its upper edge fits beneath the shoulder of the frame supporting the manhole cover, to prevent sub-surface water from entering the manhole through the regions between the manhole cover supporting frame and the top of the riser section, which is usually fitted with adjusting rings to bring the manhole cover frame up to grade. The sleeve is easily cut to any height to accommodate either a greater or lesser number of height-adjusting rings and the sleeve flange is cast into the riser section. The sleeve may be folded into itself to significantly lower its profile to expedite handling, transportation and assembly. A plastic clamping band may be placed in the interior of the sleeve to water-tightly join the upper end of the sleeve to the manhole cover support frame. A "Method and Apparatus For Lining Manhole Assemblies and the Like" is detailed in U.S. Pat. No. 4,751,799, dated June 21, 1988, also to Jack Ditcher, et al. The method and apparatus described in this patent provides liners in manhole assemblies, each of which liners includes a plurality of liner sections joined to form the inner corrosion-resistant surface of each manhole member. The liner sections define the inner surface of the manhole member being molded and cast material is poured into the mold and allowed to set. A liner surface engaging the cast material contains integral, substantially T-shaped projections which anchor the liner sections to the cast member. The tops and bottoms of each liner section extend around the surface of each section, engaging the next adjacent section joined thereto, to prevent toxic materials from reaching a cast material. The liner sections are thermoplastic vacuum formed, whereby the sheet forming the liner section is drawn against substantially T-shaped strips arranged upon the bowl member within the vacuum thermo-forming equipment to provide the integral T-shaped anchoring projections. A "Manhole Sealing Device" is detailed in U.S. Pat. No. 4,305,679, dated Dec. 15, 1981, to Arvind O. Modi. The manhole sealing device is designed to prevent water from entering a manhole through the corbel joint between the manhole casing and the cover frame. The device includes a flexible, tube-like membrane spanning the corbel joint of the manhole and provided with first sealing means above the corbel joint to seal the membrane against the inside wall of the cover frame and second sealing means located below the corbel joint to seal the flexible membrane against the inside wall of a manhole casing. That portion of the membrane located between the first and second sealing means is preferably provided with sufficient slack to form an inward fold defining an annular pocket to contain any water or other fluids entering the manhole through the corbel joint. In a preferred mode of the disclosed invention, the membrane is characterized by a bag having a closed bottom to catch water entering the manhole through or around the manhole cover. The manhole sealing device can be installed in an existing manhole without replacing any of the structural parts.
It is an object of this invention to provide a new and improved method and apparatus for sealing manholes, which apparatus is designed to utilize a removable manhole insert and a specially designed seal structure built into the manhole, for eliminating, or at least minimizing undesirable surface rainwater, sub-surface storm water and sub-surface ground water from entering a manhole and sanitary sewer system through cracks or openings in the manhole structure.
Another object of the invention is to provide a manhole seal apparatus for installation in a manhole, in order to close and substantially seal the manhole to prevent rainwater from flooding a sewerage system communicating with the manhole and vent sewer gases.
Yet another object of the invention is to provide a method and apparatus for sealing manholes which is characterized by a donut-shaped seal structure constructed in the manhole chimney, cone or base and adapted for receiving a removable manhole insert which is characterized by a dish-shaped, flanged bowl, in order to prevent, or at least reduce the flow of rainwater, including surface and sub-surface rainwater, into the manhole and the underlying disposal system.
A still further object of the invention is to provide a new and improved method and apparatus for sealing manholes by utilizing a manhole seal which is capable of sealing manholes having both concentric and eccentric cones. The manhole seal is characterized by a donut-shaped masonry ring or seal structure seated in the manhole chimney, cone or base and a dish-shaped manhole insert removably mounted in the seal structure, in order to block the flow of water into the manhole through deteriorated masonry, and yet facilitate normal manhole maintenance by removal of the manhole insert from the seal structure.
Still another object of this invention is to provide a method and apparatus for sealing new and old manhole structures from encroaching surface and sub-surface water, which apparatus includes a manhole seal characterized by a donut-shaped or elliptically-shaped seal structure formed by pouring concrete in an annulus created by a resilient, removable mold seated on a resilient form base located in the manhole chimney, cone or base and bolted to the manhole wall. A removable manhole insert having a concave dish and a rim adapted for seating on the seal structure, is installed to complete the manhole seal and block the flow of water into the manhole and the underlying sewer system.